This invention relates in general to electrical motors for submersible pumps, and in particular to a bearing for maintaining the shaft of the rotor in alignment.
High volume wells, such as for oil or water production often use a submersible pump. The pump is a centrifugal pump having a submersible motor that rotates a shaft to drive the pump. Often the motors have several hundred horsepower and are from 6 to 60 feet in length. Each motor has a stator secured within a tubular housing. A rotor secured to a shaft rotates within the stator.
Because of the long length, the rotor is made up of a number of sections. Each section comprises a large number of flat disks (laminations) secured by copper rods. The sections are spaced apart from each other, and a bearing is located between each section for maintaining the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation therewith, but are axially movable with respect to the shaft.
Each bearing assembly includes a sleeve keyed to the shaft for rotation therewith. A bearing has a bore for rotatably receiving the sleeve. The bearing has a periphery that frictionally engages the inner wall of the stator at operating temperatures to prevent the bearing from rotating. In the prior art, the sleeve length is approximately 1/16 an inch greater than the bearing length. An upper thrust washer is carried between the bottom of a rotor section and the upper edges of the sleeve and bearing. A lower thrust washer is carried between the lower edges of the sleeve and bearing and the lower rotor section. The thrust washer thus carries and transmits any force being exerted from one rotor section to the next rotor section. In large motors, the combination of the weight of the rotor sections above each bearing and high operating temperatures may cause the thrust washer to eventually deform. This may cause the bearing to spin with the rotor, possibly damaging the stator inner wall.